Mad cow is back, albeit briefly. The disease made infamous by a huge outbreak in Britain in the 1980s and early '90s popped up again this week, this time in California. It's the first U.S. case of mad cow disease in six years. After this week's discovery, the USDA quickly announced that this infected cow did not enter the country's meat supply.

James Culler is director of the University of California Davis Dairy Food Safety Laboratory. He's an authority on dairy cattle and dairy farming and he joins us now.

Welcome to the program.

JAMES CULLER: Well, thank you for having me. I appreciate it.

SIEGEL: And tell us, how did officials catch this particular case of mad cow disease?

CULLER: This was detected during the routine surveillance program that they have in place with the California Department of Food and Agriculture.

SIEGEL: And the cow in question - tell us about the animal and why we shouldn't worry about it, according to USDA.

CULLER: OK. This animal has the atypical or the spontaneous form, which is much more rare occurrence and it presents differently. It's still - the prion is refolded in a particular way that it's still contained and confined to the brain tissue, spinal cord and ganglia and is not in the milk or meat. But the animal presents as more of a downer cow, more docile and still easily picked up.

SIEGEL: You used the word spontaneous to describe this particular form of mad cow disease. That sounds almost medieval. The disease somehow just happens inside the brain. It isn't contracted from food or contact with something?

CULLER: No. This particular form is exactly like you described it. It's spontaneous. It happens in nature. It's a random event that happens on rare occasions.

SIEGEL: So, coming up with such an animal in a spot check would be something very rare. The odds would be very much against this, I should think.

CULLER: Well, the odds are very much against us seeing it on a frequent basis, but the routine monitoring system did pick it up and so we know that it's not the classical form, so we know that our things that we do to protect and detect are in place and working. In fact, it works so well, we were able to find this more rare form of the disease.

SIEGEL: But when you turn up an example of something so rare, it would seem reasonable one might check and recalculate the odds. Is it possibly more common than we thought it was?

CULLER: Well, you're right in that we found it now and so the regulatory officials and mathematicians and statisticians will re-look at this, evaluate it and then see if there are any adaptations or changes in our monitoring system need to be made. And so they're working through that process now and I'm very comfortable with how they're going to work through this.

SIEGEL: Well, James Culler of the University of California Davis Dairy Food Safety Laboratory, thanks a lot for talking with us.

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